1. Field of the Invention
The present invention relates to polypeptides which are useful for development of a reagent for clinical diagnosis or research in pathophysiology. More particularly, it is concerned with polypeptides useful for etiological diagnosis or pathophysiological investigation for cardiovascular disorders such as essential hypertension.
2. Description of the Prior Art
Recently, Kangawa, Matsuo, et al., have isolated a polypeptide [.alpha.-human Atrial Natriuretic Polypeptide=.alpha.-hANP] which has a strong natriuretic effect from the human atrium, and identified the structure which is composed of the 28 amino acids as represented by the following structure [Biochem. Biophs. Res. Comm. 118 131 (1984)]. ##STR1## It is reported that the diuretic effect of .alpha.-hANP in a biological test using rats is about 1,500 times as potent as that of furosemide which has been used frequently as antihypertensive diuretic. Although some small fragments of the .alpha.-hANP [hereinafter sometimes represented by .alpha.-hANP-(1-28)], for example, .alpha.-hANP-(7-28) [docosapeptide composed of the amino acids of the seventh to twenty eighth from the N-terminal, hereinafter referred in the same manner], .alpha.-hANP-(13-28), .alpha.-hANP-(18-28) are now commerically available, their physiological effect and their function as an antigen have not yet been reported in any literature. Among these peptides, .alpha.-hANP-(18-28) is a pyro-form peptide of which the N-terminal glutamine is cyclized, and the .alpha.-hANP-(18-28) of which the N-terminal glutamine is not cyclized is still unknown.